A turbine engine has a compressor section, a combustor section and a turbine section. In operation, the compressor section can induct air and compress it. The compressed air can enter the combustor section where it can be mixed with fuel. The air-fuel mixture is ignited, thereby forming a high temperature working gas. The high temperature working gas is routed to the turbine section where it passes rows of stationary airfoils, known as vanes, alternating with rows of rotating airfoils, known as blades.
The turbine blades and vanes are exposed to these high temperatures. Consequently, these components require cooling to prolong their life and reduce the likelihood of failure as a result of excessive temperatures. FIG. 1 shows a typical turbine blade 1. The turbine blade 1 has a root portion 2 and a platform 3. An elongated airfoil 4 extends radially outward from the platform 3. A transition region 5 between the airfoil 4 and the platform 3 is typically configured as a fillet 6. It should be noted that turbine vanes also typically include a fillet in the transition region between the airfoil and the shroud.
The fillet 6 is one area of the blade 1 that is particularly difficult to cool because of several factors. The fillet 6 is subjected to high centrifugal forces during engine operation. In order to handle such forces, the fillet 6 is generally thicker than neighboring sections of the platform 3 and of the airfoil 4. However, the greater material thickness in the region of the fillet 6 can result in high thermal gradients. The outside surface of the fillet 6 is very hot because it is exposed to the hot gases in the turbine flow path; however, the inside portion in the region of the fillet 6 is cooler due to the relatively large material thickness. As a result of such thermal gradients, the fillet 6 can experience high thermal-induced stresses. Consequently, these high stresses can cause the fillet region to be a common failure area in turbine blades.
Thus, there is a need for a system that can effectively cool the fillet region of a turbine airfoil and/or minimize high thermal gradients in the fillet region of a turbine airfoil.